German document DE 197 07 587 B4 discloses an electromagnetic control element with a pole tube which contains an armature that can be actuated by means of a solenoid coil, and comprising a pressure tube into which a ferrite core has been inserted. The position of the ferrite core relative to the pressure tube can be picked up by means of measuring coils provided along the outer circumference of the pressure tube. The pressure tube has a thickened flange that is joined to a magnetically conductive part of the pole tube by rolling it at an attachment site. In the state of the art, such pressure tubes are often manufactured by lathing a blank.
As an alternative to manufacturing the lathed part from a blank, it can be configured as a tube and sealed using a soldering or welding technique. For instance, U.S. Pat. No. 6,605,940 B1 discloses a tube that accommodates an armature, whereby the axial end of this tube is sealed off by a plug.